[meteorite-list] Meteor Impact Trapped Ancient Swamp Plants in Glass

[Ron Baalke]

http://www.newscientist.com/article/dn24560-meteor-impact-trapped-ancient-swamp-plants-in-glass.html 

Meteor impact trapped ancient swamp plants in glass
By Lisa Grossman
New Scientist
November 11, 2013
	 
Remnants of an ancient swamp have been found preserved inside glass created 
during a meteorite strike. The discovery marks the first time that traces 
of life have been found to survive the heat and pressure of an impact, 
adding weight to arguments that microbes travelling on space rocks could 
have seeded the solar system.

Astrobiologists have long suggested that simple life forms could have 
hitched a ride to Earth inside meteors, or that impacts on early Earth 
could have sent terrestrial microbes to other worlds on ejected pieces 
of our planet. We know that rocks kicked up by impacts can travel vast 
distances. Martian meteorites with soil trapped inside have landed on 
Earth, and theoretical calculations suggest that meteor strikes on Earth 
could have had enough energy to send rocks as far away as the moons of 
Jupiter and Saturn.

But this concept, called panspermia, also assumes that the organic compounds 
essential to life as we know it can survive the extreme pressures and 
temperatures of a crash-landing. Now, evidence has been found around Darwin 
crater in Tasmania, which was formed by an impact about 800,000 years 
ago.

Swamp life

Glass created when rock melted during the impact is strewn in a 
400-square-kilometre field around the crater. Kieren Torres Howard was 
conducting doctoral research at the University of Tasmania in Hobart, 
Australia, studying the distribution and composition of the impact glass. 
Taking a closer look with an X-ray diffraction machine, he found that the 
glass is unexpectedly shot through with tiny spherical inclusions. The 
glass is also riddled with geometrically regular pockets, like a honeycomb.

Howard and colleagues ground up the glass and sorted through the fragments 
with an acupuncture needle to pick out the inclusions, the largest of 
which was about 200 micrometres across. Chemical analysis showed that 
the inclusions were rich in organic material similar to that in a peat 
swamp, including cellulose and polymers that might derive from leaf cuticles.

"They looked really pristine," says Howard, who is now at the City University 
of New York in Brooklyn. "It's not just that you see a signature of organic 
materials, it's almost as if you took the signature of a swamp today." 
Previous evidence found at the crater site, including a species of burrowing 
crayfish that has probably lived in the area for the past million years, 
had suggested that the region was a swamp or rainforest when Darwin crater 
was formed.

"That's what allowed us to really believe we'd found some organics. We 
knew this was a swamp impact," says Howard. The team think that a meteor 
smacked into the ground and melted some of the upper rock to form the 
impact glass. Bits of plant matter found its way into the molten glass 
as everything was hurled away by the impact. The water and other volatile 
compounds in the plants immediately boiled, making a bubbling froth that 
froze inside the glass as it cooled, creating the honeycomb of pockets.

Funky implications

"I think it is well argued, and they made a very interesting discovery," 
says Christian Koeberl of the Natural History Museum in Vienna, Austria, 
who was not involved in the new work. "It is the first time to my knowledge 
that organic  material has been found preserved in such a way within impact 
glass."

So could pieces of an ancient swamp on Earth have gone flying off into 
space? It's plausible, the team says, and organics trapped inside glass 
would be somewhat protected from cosmic radiation on an interplanetary 
journey. "That's when the implications get much more funky," says Howard. 
"There's not much challenge in dispersing this stuff. Some material might 
end up on the moon, some might end up on Mars. The material would be ejected 
into space in a well-preserved state."

NASA's Curiosity rover may have already found Martian impact glass at 
its home in the Red Planet's Gale crater, according to a presentation 
at the Geological Society of America meeting in Colorado last month. Curiosity 
doesn't have the dexterity to pick up these shards and run analyses on 
them, says John Mustard of Brown University in Providence, Rhode Island. 
But such glasses could be good targets for future sample-return missions 
aiming to bring Mars rocks back to Earth. Scientists here could then run 
tests to see if terrestrial material has landed on Mars, or if the glass 
contains preserved traces of long-lost Martian vegetation.

"Could it have been the mechanism by which panspermia happened? Sure," 
says Mustard. "It allows the packaging and interplanetary transfer of 
organic material."

Journal reference: Nature Geosciences, DOI: 10.1038/ngeo1996